What’s a Healthy BMI in Adults? Here’s Everything You Need to Know

A “healthy” BMI varies on the basis of several factors, including sex and age.

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BMI stands for body mass index, but you'll almost always find it referred to simply as BMI. It’s an estimate of how much body fat a person has, and it's calculated by dividing a person's weight in kilograms by his or her height in square meters. (1)

Don’t be intimidated by the number crunching — there are loads of online calculators that will generate your BMI when you put in your stats. (2) The resulting number can help you determine whether you’re at a healthy weight. Here’s what your number means:

BMI has long been a popular tool for measuring body fat because it’s easy to use and doesn’t require any fancy equipment to calculate. There’s a downside to that simplicity, though: It sometimes delivers an oversimplified picture of your health (more on that later).

But as the Centers for Disease Control and Prevention (CDC) notes, there are a few differences among certain demographics when it comes to body fat. (3)

Women usually have more body fat than men. According to the AARP, women should aim for 20 to 21 percent body fat, while men should have between 13 and 17 percent. (4)

Black people usually have less body fat than white people, and Asians typically have more than white people.

Older people generally have more body fat than younger people.

Athletes usually have less than nonathletes.

BMI tends to be problematic among older people, Jaelin says. According to one study, BMI isn’t as useful in older adults because it doesn’t account for the fact that many people get shorter as they age, which can lead to underestimated fat levels. (5) BMI also can underestimate fatness among seniors because as people age, fat mass usually replaces fat-free mass (muscle). So while an older adult may clock a normal BMI, he or she could have a high body fat percentage. The researchers call this “normal-weight obesity,” which puts people at an increased risk for metabolic syndrome and a variety of cardiovascular issues.

These discrepancies have led some researchers to suggest that BMI targets should be different for older adults. One meta-analysis explored the relationship between BMI and risk of death among people 65 and older and found that the lowest risk of death was among people with a BMI of around 27.5 — which qualifies as overweight. (6) The study found that in older people a BMI between 22 and 23 actually increased the risk of death, even though it's in the normal range.

Why Having a Healthy BMI Matters for Your Overall Health

Is BMI just another number to keep track of? Not exactly. It can be useful in telling you whether your weight is in a healthy spot, and if your BMI has fallen outside the normal range it clues you in when you may be at risk for various health conditions.

A BMI of 30 or higher, for instance, means you qualify as obese, which can lead to: (3)

Many worrisome issues come with being big. “As your BMI goes up, you start developing fat mass problems,” says Eduardo L. Grunvald, MD, a board-certified internal medicine doctor with UC San Diego Health System and the director of the UC San Diego Weight Management Program in California. “You start getting the joint problems, the sleep apnea, the acid reflux, those kinds of issues that are directly related to just mass.”

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Being underweight (with a BMI of less than 18.5) presents its own set of challenges. One study found it can contribute to an increased risk of dying, though those deaths are more likely to be the result of unnatural causes (such as accidents or suicide) rather than cancer, cardiovascular disease, or respiratory disease. That may be because underweight people are at an increased risk of injury and, once injury occurs, they usually have a harder time recovering. (7)

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What Are the Flaws of Measuring BMI in Adults?

BMI is not a perfect metric and should only be used as a preliminary tool to determine if you’re at a healthy weight, Jaelin says. “The problem with BMI is it doesn’t say anything about body fat composition, body fat distribution, or metabolic consequences,” Dr. Grunvald says. “It’s just purely weight compared to height.”

So don’t panic if your BMI signals you’re overweight or obese, but rather take it as a hint that it’s time to see a physician for a more thorough assessment. “BMI was designed to look at a large number of people, but you have to dive deeper and not look just at BMI” to know for sure whether you need to be concerned, Grunvald says.

The CDC suggests measuring your waist circumference as another way to estimate your risk of developing weight-related health conditions, such as type 2 diabetes, high blood pressure, and coronary artery disease. (8) To measure yours, place a measuring tape right above your hip bones. Keep it snug but not too tight, and take the measurement right after you exhale. A circumference larger than 35 inches for women and 40 inches for men indicates you’re at an unhealthy level.

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Some researchers are proponents of taking it a step further and measuring waist-to-hip ratio. One study looked at more than 15,000 adults and found normal-weight central obesity, as determined by waist-to-hip ratio, was linked to higher mortality rates than obesity as defined by BMI. (9)

Another popular way to determine if you’re at a healthy weight is by using the Hamwi method. Here’s how it works, per the AARP: (4)

For women, take 100 pounds (lb) for the first 5 feet of height. Then add 5 lb for each additional inch to reach the ideal weight.

For men, take 106 lb for the first 5 feet of height. Then add 6 lb for each additional inch.

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How to Reach a Healthy Weight if You’re Overweight or Obese

Jumping from a high BMI to a lower, healthier number can seem daunting. But losing just 5 to 10 percent of your body weight has been shown to counter the negative side effects and improve your blood pressure, blood cholesterol, and blood sugar — even if you still fall into the obese category post weight loss, according to the CDC. (10)

It’s tough to say exactly how to reach a healthy weight, because there isn’t a one-size-fits-all answer, Jaelin says. The best way to get personalized recommendations, she says, is by consulting a dietitian or a doctor.

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You can also start to lower your BMI (or raise it, if you’re underweight) by adopting these six healthy habits:

1. Eat Regularly

Get in the habit of eating every two to three hours. At each meal, include a palm-size amount of protein, whether it’s chicken, fish, beef, or tofu. Eat that with a fist-size portion of a carbohydrate, such as fruit, quinoa, brown rice, or whole wheat bread for a well-balanced meal, Jaelin suggests. Following this approach can promote a healthy weight.

2. Stick With Water

Don’t drink anything but water with your meal. Instead, leave room in your stomach for food, and save your fluids for outside of mealtime, advises the Academy of Nutrition and Dietetics. (11)

3. Get Creative With Nutrition

Sneak in extra calories without overhauling your diet. For example, spread peanut butter on toast, sprinkle cheese on top of chili, or use milk in your oatmeal instead of water. (11)

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4. Start Your Day Off Strong

To lose weight, Jaelin suggests starting your day with a protein- and fiber-packed breakfast. One cup of steel cut oats with ¾ cup of Greek yogurt and ½ cup berries checks all the boxes.

“The high protein from Greek yogurt stabilizes blood sugar levels to avoid sugar [and other food] cravings later on in the day, and the fiber from steel cut oats will keep you full longer,” Jaelin says.

Starting the day on a healthy note can also set the tone for the day, she says.

5. Count Your Calories

Losing 1 to 2 pounds per week has been shown to be the most sustainable rate. One way to get there is by cutting your daily calories by between 500 and 1,000. (10)

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6. Move It

Don’t discount the role of exercise in helping you reach your ideal weight, whether you’re looking to gain or lose. Consult a personal trainer to outline a plan that’s tailored to your goals.

Reaching a healthy weight (and healthy BMI) not only slashes your risk for many diseases, but it has been shown to boost your confidence, energy level, and your overall mood. That's an all-around win. (10)

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